My mondeo has a weird fault that defies the local mechanic: would like some advice on my next steps.
It runs ok, but when cruising the power drops in and out regularly - you can feel it and hear it in the revs, but the rev count barely moves actually - just a wobble if anything. It doesn't noticeably happen when accelerating or when coasting, only when cruising in gear - 40-50 mph.
It is smoking more than it used to do (I've had it a few years now) - white smoke from exhaust that comes out in puffs that coincide with the loss of power, every few seconds when holding it at a steady pace. Its like it putt-putts down the road! Also, periodically -particularly when putting down the power, (eg overtaking) - there are puffs of black smoke out the exhaust.
I thought maybe it was to do with fuel filter, but now changed and no difference. On other advice I dosed it with Redex for a few tankfulls, but that didn't do anything. Latest advice is that it might be a software fault, so I should get reloaded software at a dealership - however I'm not convinced - i still wonder if its mechanical and reloading software is an expensive red herring.
Just before all this started a fortnight ago I did notice that under power there was a new sound - like air rushing.
I don't mess under the hood myself, but want to be able to suggest something to another mechanic.